[Elecraft] Suggestions for 10 MHz Signal Source for the K3?

[Matt Zilmer]

Long term stability is in the 10^10 range, and short term one sees
<100 ppt generally.  Quite often it's stable for minutes down to 25
ppt.  The Thunderbolt is subject to GPS sats coming and going, and/or
noise from sats being too near the horizon.  Each time a sat joins or
leaves the constellation, there is a little "few ppt" bounce in the
ppt.

I did some lab measurements against our Rb sources here at Magellan.
It takes special test equipment that we don't have to be able to sense
the difference.  However, using a TIA locked to the GPSDO, the Rb
drifts in relation to the tune of +/- 50 ppt for a short term
observation.  I don't have time to run it for months, just hours at a
time.

There will always be some question about the value of accurate
frequency sources used with ham radio.  The K3 VFO has its own finite
resolution of 1 Hz, so that's the best quanta it can do anyway.
Watching the compensation using REF CAL, I can see it drift up from 
49379.690 to 49379.776 over the span of several hours.  But that's
just the compensation working against the TCXO and there is little or
no difference in pitch on air air for fixed sources like WWV or CHU.
There is no discernable beat note, since the heterodyne is below
audible frequencies.  I don't see it on the s-meter either, so it's
probably around or below 1 Hz most of the time.

The K3 makes very fine adjustments using the source, only on RX I
believe, and only every few seconds.  

The K144XV ref lock is still tied to the TCXO , not the external
reference.  Dunno what the plan is to change this, but the TCXO-1 is
so much better than the xx PPM crystal injection oscillators at 116
and 118 MHz that it's remarkable.  Maybe not yet good enough for
microwave work, but much better on 2m.

73,
matt W6NIA



On Tue, 21 Jun 2011 06:33:42 -0700, you wrote:

>On 6/20/2011 11:35 PM, Matt Zilmer wrote:
>
>> I'm using the Trimble Thunderbolt here, with good results.  I ordered
>> two units from one of the eBay vendors.  These shipped from within the
>> US and were less than $80 each.
>
>  What are the stability and accuracy of these devices in parts
>  per billion (10^12)?  For 80 bucks you're not going to get a
>  rubidium or cesium standard, and zero-beating WWV will only
>  give you 1 part in 10^7 for a one-second measurement.
>
>  (Pardon my cynicism - my former network frequency standard
>  needed something like 1 part in 10^12 to do the job right.)
>
>--  73 de K2ASP - Phil Kane
>    Elecraft K2/100   s/n 5402
>
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